Illegal detention means police hold you without a good reason. In California, the law is strict.If you had an arrest that did not result in a conviction, you may be able to seal your case under Penal Code section 851.91. The district attorney will then file a Petition, usually within 2 days after the arrest. If you have been arrested and no charges are filed against you, the arresting agency must reduce your arrest to a detention and send you documentation of such. No, a detention is not an arrest. If you were held in detention and then released, you should not expect charges to be filed. The limit is attuned to the type and progress of the investigation. 15–20 minutes on a traffic stop for a minor traffic violation. A Certificate of Detention (Penal Code Section 851.6) may be the best and fastest remedy to "clean up" your arrest record.